1. Field of the Invention
The present invention relates to a method for manufacturing a terminal with an electric wire, in which a sealing portion such as an anticorrosion portion is formed in a connection part where different kinds of metals are connected to each other between the electric wire and a terminal fitting.
2. Description of Related Art
A wire harness is wired in a vehicle, for example, in order to establish electric connection between devices mounted on a car. The wire harness is configured to include an electric wire bundle, and various connectors disposed at terminal ends of the electric wire bundle. Each connector for the wire harness is configured to include an insulating connector housing, and a plurality of conductive terminal fittings received in terminal reception chambers of the connector housing. The terminal fittings are disposed at terminal ends of electric wires constituting the electric wire bundle. Copper electric wires (whose conductors consist of stranded wires made of copper or a copper alloy) are generally used as the electric wires. The terminal fittings are crimped and connected to terminal ends of the copper electric wires from which coatings have been removed. Incidentally, a base material of the terminal fittings is made of copper or a copper alloy in the same manner as the conductors of the copper electric wires. Plating may be applied to the terminal fittings.
In recent years, aluminum electric wires (electric wires whose conductors are made of aluminum or an aluminum alloy are referred to as aluminum electric wires herein) may be used in place of copper electric wires in consideration of weight reduction of a vehicle and easiness in recycling materials as well as shortage of copper resources. However, it has been known that an oxide film formed in the surface of an aluminum electric wire is thicker than that in the surface of a copper electric wire whose conductor is made of copper, and contact resistance between a conductor of the aluminum electric wire and a terminal fitting (crimping terminal) is apt to be comparatively higher. Therefore, in order to reduce the contact resistance between the conductor of the aluminum electric wire and the crimping terminal, the following method is used. That is, a pair of conductor crimping pieces are formed in the crimping terminal, and the conductor is strongly crimped by the conductor crimping pieces to increase a compression rate. According to this method, the conductor of the aluminum electric wire is strongly crimped so that an oxide film on each of strands constituting the conductor can be broken. That is, the contact resistance between the conductor and the crimping terminal can be reduced.
However, it has been known that when water intervenes in a contact part between an aluminum material and a copper material or, to say other words, in a contact part between different kinds of metals, both the metals, that is, aluminum and copper are dissolved into the water as ions so that electric corrosion can occur due to a potential difference or the like between the both. Incidentally, when a conductor of an aluminum electric wire and a crimping terminal made of copper or a copper alloy are electrically and mechanically connected to each other, the conductor is crimped with a high compression rate by conductor crimping pieces of the crimping terminal so that water immersion can be prevented in the crimping part where the conductor is crimped, with the result that occurrence of electric corrosion can be avoided. However, in a position in an axial direction of the terminal (in an extending direction of the electric wire) with respect to the crimping part where the conductor is crimped by the conductor crimping pieces, the conductor is exposed partially. Therefore, when water adhering to the exposed part of the conductor reaches the crimping part, the crimping part becomes a state as if it were immersed in an electrolytic solution. Thus, there is a fear that aluminum that is a metal having a higher ionization tendency may be dissolved to advance electric corrosion. As a solution, in order to prevent water from adhering to the exposed part of the conductor or from entering into the crimping part, an anticorrosion portion 115 (sealing portion) is formed in the background art as shown in FIGS. 9A and 9B (for example, see JP-A-2011-113708).
In FIGS. 9A and 9B, the reference numeral 101 represents an aluminum electric wire, and the reference numeral 102 represents a crimping terminal. The aluminum electric wire 101 is configured to include a conductor 103 made of aluminum or an aluminum alloy, and an insulating resin coating 104 covering the conductor 103. An end portion of the resin coating 104 is removed from the aluminum electric wire 101. Thus, a conductor exposed portion 105 is formed. On the other hand, the crimping terminal 102 is a female type terminal fitting, which is formed into the illustrated shape by pressing of a metal plate made of copper or a copper alloy. The crimping terminal 102 includes a rectangular cylindrical electric contact portion 106, a crimping portion 107, and a coupling portion 108 that couples the electric contact portion 106 and the crimping portion 107 with each other. A mounting portion 109, conductor crimping pieces 110 and coating crimping pieces 111 are formed in the crimping portion 107. The conductor exposed portion 105 is mounted on the mounting portion 109. The conductor exposed portion 105 mounted on the mounting portion 109 is crimped by the conductor crimping pieces 110. The resin coating 104 near the conductor exposed portion 105 is crimped by the coating crimping pieces 111.
In the above-described configuration and structure, a wire-terminal connection portion 118 is formed including a conductor crimping part 112 in which the conductor exposed portion 105 is crimped by the conductor crimping pieces 110, and a coating crimping part 113 in which the resin coating 104 near the conductor exposed portion 105 is crimped by the coating crimping pieces 111. Incidentally, in the conductor crimping part 112, a non-crimping part 114 is produced due to the relationship between the length of the conductor exposed portion 105 and the width of the conductor crimping pieces 110. Therefore, the anticorrosion portion 115 (sealing portion) is formed in the wire-terminal connection portion 118 so as to cover the non-crimping part 114. The anticorrosion portion 115 is formed of an anticorrosive material 117 (sealing material) dropping from respective nozzles 116 of two dispensers. The anticorrosive material 117 applied by dropping is then cured. Thus, the anticorrosion portion 115 is formed. Incidentally, silicone rubber is used as the anticorrosive material 117.